1. Field of the Invention
The present invention relates generally to electrical switching apparatus and, more particularly, to a trip indicator for a circuit breaker. The invention also relates to circuit breakers including a trip indicator.
2. Background Information
Circuit breakers are generally old and well known in the art. Examples of circuit breakers are disclosed in U.S. Pat. Nos. 5,341,191 and 5,471,184. Circuit breakers are used to protect electrical circuitry from damage due to a trip condition, such as, for example, an overcurrent condition, an overload condition, an undervoltage condition, or a relatively high level short circuit or fault condition. Molded case circuit breakers, for example, include at least one pair of separable contacts which are operated either manually by way of a handle disposed on the outside of the case, or automatically by way of a trip unit in response to the trip condition.
Circuit breakers typically have two or three operating handle positions corresponding to the status of the separable contacts. For example, a three position breaker may include an ON position in which the separable contacts are closed, an OFF position in which the contacts are open, and a tripped position in which the contacts are tripped open. Typically, the handle position corresponding to the tripped position of the contacts is between the ON and OFF positions. However, this is not always the case. In two-position breakers, the tripped operating handle position is shared with the OFF position. Specifically, when the trip condition occurs and the circuit breaker trips, the operating handle is automatically forced to the OFF position. It is difficult to quickly visually determine the status of such circuit breakers. This is problematic and it is even more pronounced when the circuit breaker is only one of a plurality of circuit breakers arranged within the same panelboard or switchboard perhaps with several breakers already intentionally turned OFF. Under such circumstances, it is nearly impossible to determine which circuit breakers have tripped because the operating handle appears in the same position as it does for the breakers which have been intentionally turned OFF.
To help alleviate this problem, known circuit breaker designs employ a variety of trip and status indicators. For example, it is known to provide a trip flag in the circuit breaker to indicate the tripped condition. Generally, the trip indicator comprises an indicator assembly which interacts with the operating handle or cradle of the circuit breaker in order to position a visual indicia, such as the trip flag, or printed words indicative of the circuit breaker status (e.g., “T”, “TRIPPED”, “ON” or “OFF”), beneath a lens or window which covers an opening in the circuit breaker housing. Typically, the flag or other indicia is actuated, in response to the trip condition, by the cradle. For example, when the cradle unlatches in response to the trip mechanism and pivots, the separable contacts of the circuit breaker are opened. The flag is then reset by relatching the cradle through movement of the operating handle. However, the trip indicia of such indicators are somewhat concealed within the opening in the circuit breaker housing and often can only be clearly seen when viewed from a very close range and substantially straight on through the lens or glass window. This is disadvantageous because, in most circuit breaker applications, many of the circuit breakers are located or positioned at an elevation other than at eye level, thus limiting the effectiveness of the indictor.
Additionally, as previously discussed, in most known trip indicators, the indicator assembly interacts with the operating handle in such a manner that the visual indicia moves therewith. See, e.g., U.S. Pat. No. 6,246,304. Therefore, one can easily reset the circuit breaker from the tripped position by merely moving the operating handle back to the ON position. This is undesirable under certain circumstances where it is advantageous to prevent the breaker from being arbitrarily reset. For example, it is frequently important to evaluate the cause of a circuit breaker trip (e.g., identify the source of the abnormal current condition) before any necessary repairs or corrections can be made in order to resolve the problem. Otherwise, the breaker might continue to trip or damage could occur to electrical equipment in communication with the circuit breaker.
There is a need, therefore, for a trip indicator which provides a visual indication of a tripped circuit breaker condition which can be quickly and easily seen from a variety of viewing positions, and for providing a trip indicator capable of simultaneously locking the breaker in the tripped position in order to, for example, provoke some thought as to why the breaker tripped before simply resetting the handle.
There is, therefore, room for improvement in trip indicators for circuit breakers and in circuit breakers employing trip indicators.